Flash boiler

ABSTRACT

A flash steam boiler utilizing a solid metallic core wherein the heat exchange passageways are drilled, the hot gas openings extending perpendicularly through the core with the water passages winding in a dual serpentine path through the core so as to contact both sides of the metal surfaces surrounding each gas passageway. The cores can be stacked so as to exchange heat between the gas flow and the serpentine path at a plurality of discreet levels. Because the cores are metallic, the ends of at least one core in each boiler is provided with a sensing plate which is caused to move by thermal expansion of the entire core toward a plurality of microswitches controlling the operation of the boiler, each of the microswitches being activated at a different amount of thermal expansion of the core.

United States Patent Hoch [451 Jan. 18,1972

1541 FLASH BOILER Earl W. Hoch, RR. #3, Petoskey, Mich. 49770 221 Filed:May 21,1970

21 Appl.No.: 39,265

[72] Inventor:

1,234,548 7/1917 Kleinfeldt ..l65/39 Primary Examiner-John J. CambyAttorney-Price, Heneveld, Huizenga & Cooper [5 7] ABSTRACT A flash steamboiler utilizing a solid metallic core wherein the heat exchangepassageways are drilled, the hot gas openings extending perpendicularlythrough the core with the water passages winding in a dual serpentinepath through the core so as to contact both sides of the metal surfacessurrounding each gas passageway. The cores can be stacked so as toexchange heat between the gas flow and the serpentine path at aplurality of discreet levels. Because the cores are metallic, the endsof at least one core in each boiler is provided with a sensing platewhich is caused to move by thermal expansion of the entire core toward aplurality of microswitches controlling the operation of the boiler, eachof the microswitches being activated at a different amount of thermalexpansion of the core.

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sum 6 or 7 INVENTOR EARL W, HOCH BY M ATTORNEYS PATENTEUJANIBIHYE $535 24 INVENTOR EARL W. HOCH ATTORNEYS 1. FLASH BOILER BACKGROUND or THEINVENTION To convert water into steam," it is customary to utilize aboiler wherein the heat from gases of combustion is transferred to thewater. A problem with boilers today and particularly when used withautomobiles is to construct them so as to operate efficiently, at thesame time occupying a minimum amount of space, and yet be controlledautomatically. The use of a boiler to drive an automobile requires thatthe water be converted to steam at the proper pressure as soon aspossible. This is best accomplished, for purposes of efficiency, byextracting as soon as possible as much heat as possible from the hotgases of combustion. The further use of a boiler in an automobilerequires that no manual switching of the boiler be necessary other thanturning it on and off."

It will be apparent then that one problem is to provide maximum contactbetween the water and the surfaces of the pipes or other conductorscarrying the hot flue gases, at the same time minimizing the amount ofspace such construction requires, in such a way as to allow the boilerto be automatically operated.

Other problems particularly pertinent to flash boilers is the presenceof hot spots due to uneven heating, and the high pressure necessarilygenerated by the boiler under the best of conditions. Both of theseproblems have required very meticulous manufacturing standards, thusincreasing the cost of flash boilers.

SUMMARY OF THE INVENTION This invention relates to a flash boiler andthe heat exchanger utilized in the flash boiler which achieves a maximumemciency with a minimum of space and cost and with automatic controls.Specifically, the invention provides improvements in a heat exchangerutilizing passageways for carrying both a hot and cold medium for theexchange of heat therebetween, one improvement including the passagewaysfor one of the mediums being positioned to confine the flow of thatmedium to a nonlinear path which contacts the exchanging surfaces ofsubstantially all of the passageways for the other of the mediums on atleast two opposite sides thereof. The contact on the two oppositesurfaces of each of the passageways for the other of the mediumsprovides maximum contact, particularly when the passageways of the heatexchanger are confined to a planar core. This improvement also includesthe use of a plurality of cores stacked together, the planar nature ofthe cores allowing them to be stacked parallel to each other with aminimum of space therebetween. With such a construction, the confinementof the flow of the one medium to a nonlinear path can contact theaforesaid surfaces of each of the passageways for the other of themediums at a plurality of points discontinuously spaced along the lengthof each of the aforesaid surfaces. To this end, the nonlinear pathrepresenting the confinement of the one medium is a serpentine pathwhich contacts all of the passageways for the other of the mediums ineach of the cores, one core at a time, moving in a direction to maintaina maximum temperature differential between the two mediums.

A further improvement comprises the use of positive direct sensing ofthe core of the exchanger to determine the temperature limitations ofoperation of the core. This is accomplishcd by positioning sensing meansadjacent to the end of the core for sensing dimensional changes of thesame due to the operation of the exchanger, and providing controllingmeans operatively connected to the sensing means for controlling theamounts of hot and cold mediums to be supplied to the passageways of thecore in response to the sensed dimensional changes of the core.

Still another improvement'utilizes the wrapping of the core about itselfin a cylindrical manner so as to confine the combustion chamber withinthe core.

Accordingly, it is an object of the invention to provide a heatexchanger in a flash boiler which. by drastically increased contactbetween the heat-exchanging surfaces of both mediums, a maximumefficiency utilizing a minimum of space is obtained.

It is another object of the invention to provide a heat exchanger of theabove character wherein a maximum amount of heat is extracted from theheat source by repeated contact with the heat sink in a minimum amountof space necessary for this end.

It is a related object of the invention to provide a heat exchanger ofthe above character wherein a positive and direct control is obtainedover the operations by sensing the dimensional changes in the core ofthe exchanger.

It is further object of the invention to provide a heat exchanger of theabove character wherein the heating is uniform, without requiringexpensive manufacturing techniques.

Other objects and advantages willbecome apparent upon reference to thefollowing drawings and detailed discussion.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a partially explodedperspective view of a flash boiler constructed in accordance with theinvention;

FIG. 2 is a fragmentary sectional view taken along the line II-II ofFIG. 1;

FIG. 3 is a fragmentary sectional view taken along the line IIIIII ofFIG. 1;

FIG. 4 is a fragmentary bottom view taken along the line IV-IV of FIG.1;

FIG. 5 is a fragmentary perspective view with portions broken away,showing the details of the supporting rod illustrated in FIG. 1;

FIG. 6 is a fragmentary, partially sectioned and broken away,elevational view of the control end of the boiler illustrated in FIG. 1;

FIG. 7 is a partially schematic plan view of the boiler of FIG. 1,illustrating its position in the flue pipe;

FIG. 8 is a schematic diagrammatic view illustrating the control of theboiler;

FIG. 9 is a front elevational view of a plurality of flash boilerssimilar to that shown in FIG. 1 through 7 positioned in a stackedarrangement;

FIG. 10 is a plan view of the arrangement shown in FIG. 9;

FIG. 11 is an end elevational view with the insulating wall removed forclarity, of the arrangement shown in FIG. 9, taken generally along theline XIXI;

FIG. 12 is a sectional view taken along the line XII-XII of FIG. 10, theinsulating wall having been removed for clarity;

FIG. 13 is a sectional view taken along the line XIII-XIII of FIG. 10;

FIG. 14 is a sectional view taken along the line XIV-XIV of FIG. 9;

FIG. 15 is a sectional view taken along the line XVXV of FIGQ10;

FIG. 16 is a perspective view of an alternate embodiment of the flashboiler of the invention; and

FIG. 17 is a sectional view taken generally along the line XVII--XVII ofFIG. 16.

DESCRIPTION OF THE PREFERRED EMBODIMENT As used throughout thisapplication, the words horizonal" and vertical" are not absolute termsbut are to be construed on the basis of the relationships depicted inthe figures illustrating the described embodiment.

The invention relates to heat exchangers and specifically to a flashboiler specifically designed for use with an automobile engine or boatengine. The flash boiler is thus designed to exchange heat from hotgases of combustion to water so as to turn the latter into steam, thesteam being utilized to drive the automobile or boat engine.

Referring to FIGS. 1 through 7, the embodiment illustrated thereinincludes a frame 20 and two stabilizing tubes 22 bolted at opposite endsof the frame 20. A core 30 is held by bolts 3| to the frame 20 betweenthe bolts holding the tubes 22, the bolts 31 passing through standofi'spacer tubes 32 which extend from the frame 20 to one end 33 of the core30. By core," it is meant a solid platelike member, preferably of metalsuch as stainless steel. It is within the core that the heat exchangingtakes place.

At the opposite end 60 of the core 30, rods 62 project therefrom andmount a sensing plate 64, which plate is provided with openings 66 (FIG.6) for sliding over the stabilizing tubes 22. The sensing plate ormember 64 cooperates with a control plate or member 80 positioned at theend of the stabilizing tubes 22 opposite to the ends joined to the frame20.

The entire arrangement is then positioned within a flue pipe 100 asshown in FIG. 7, the stabilizing tubes 22, the spacer tubes 32, the rods62, and the water inlet and outlet tubes 56 and 58 projecting throughbushings located in the walls of the pipe 100.

THE CORE Referring to FIGS. 1 through 4, the core 30 comprises aplatelike member 34 of stainless steel having a plurality of generallycircular passageways or openings 35 extending perpendicularly throughthe plate. In addition, heat exchanging passageways 44 extend throughthe member 34 in the plane of the member and perpendicularly to thedirection of the passageways 35. The portion of the core member 34between the openings 35 and 44 is the heat exchanging media of the core,the surfaces of the passageways 44 being the primary heat exchangingsurfaces in that the heat generated by gases flowing through theopenings 35 is released through these surfaces 44.

Each of the openings 35 is uniformly drilled so as to form a pluralityof horizontal rows 36 and vertical columns one of which is partiallyshown in FIG. 2. Thus, the openings 35 are nonconnecting. Each of therows 36 is recessed on both sides of the plate 34 so as to form aplurality of fins 38 between the rows.

Referring now to the passageways 44 and particularly as shown in FIGS. 1and 3, these passageways are formed by drilling two holes between eachcolumn of openings 35, the two holes drilled between each column beingparallel so as to establish a plane which is parallel to and between twocolumns of openings 35. Thus, the plane 46 defined by two openings 44provides a parallel passage for the heat exchanging medium forcedtherethrough in an upward direction as shown in FIG. 1, whereas theplane 48 defined by two openings 44 provides parallel passage for theheat exchanging medium in a downward direction as viewed in FIG. 1.

It will be readily appreciated that the uniformly spaced drilling of thepassageways 35 and 44 into a solid core greatly facilitates themanufacturing of the boiler, and provides a core which provides uniformheat expansion while retaining its strength.

Header plates 50 and 52 are welded to the edges of the core 34representing the end of the passageways 44. The headers have providedtherein on the underside thereof (FIG. 4) pairs of parallel slots 54 and55, each pair comprising one slot 54 and one slot 55 and lining up withfour openings 44. Each slot in the pair extends perpendicular to theplane of parallel openings defining one direction of travel of the heatexchanging medium. Thus, one pair of slots 54 and 55 are positioned soas to extend transversely to the planes 46 and 48, thereby linking uptwo of the passageways 44 by each of the slots. In this way, aturnaround is provided for the heat exchanging medium.

At one end of the header 50, a water inlet tube 56' is attached thereto,and at the other end of that header a water outlet tube 58 is similarlyattached.

THERMAL EXPANSION CONTROL Turning to FIGS. and 6, the sensing plate 64has mounted at the side 68 opposite to the side mounting the support rod62 a plurality of abutments 70 through 72. Each of the abutmentscomprises an adjusting screw which can be turned into the plate 64 aprescribed distance. The positions of the adjusting screws 70 through 72are such as to be aligned with the appropriate parts of the controlplate 80. Those parts of the control plate are microswitches 81, 82 and83 which control various functions and operations of the boiler ashereinafter described. The plate is fixedly mounted with respect to theflue pipe 100 inasmuch as it is floatingly mounted within thestabilizing tubes 22 by means of a spring 85 held in place in each tube22 by a threaded slug 87. The springs 85 press against one side of ears88 extending from the control plate 80. The opposite side of the ears 88is pressed against the end 90 of a carbon rod 92. Thus, whereas thestabilizing tube 22 undergoes thermal expansion, the carbon rod 92undergoes very little expansion so as to maintain the position of thecontrol plate fixed with respect to its original orientation. Incontrast, the rods 62 expand outwardly due to the expansion of the coreand of the rods themselves as the core is heated, thereby pushing thesensing plate 64 outwardly so as to bring the adjusting screws 70through 72 into contact with their respective microswitches. The plate64 is mounted via openings 66 for relative movement upon the stabilizingtubes 22 because the rods 62 tend to expand outwardly at a rate whichexceeds the expansion of the stabilizing tubes 22.

OPERATION As indicated previously, the heat exchanger is specificallydesigned as a flash boiler for driving a steam engine. Accordingly,referring to FIG. 8, when an ignition switch (not shown) is turned on,the furnace or combustion chamber 94 is activated and the hot flue gasesflow through the pipe and through the core 30 (FIG. 7). This continuesuntil the temperature of the boiler rises to between 400 and 500Fahrenheit at which time the core 30 and the rods 62 have expandedsufficiently so as to move the sensing plate 64 outwardly to the pointwhere adjusting screw 70 abuts the microswitch 81. This closes thecircuit to a first stage feed water pump 102 which operates from abattery 104, the pump supplying a relatively low volume of water from awater tank 106 to the boiler through a line 107 emptying into the inlettube 56. The water then flows through the serpentine path defined by thepassageways or openings 44, the water dividing up into the pairedpassageways and flowing first downwardly as viewed in FIG. 1 and thenupwardly on the opposite side of the first column of flue openings 35.The serpentine path continues flowing in a direction perpendicular tothe direction of flow of combustion gases through the flue openings 35,the latter being designated by the arrow 108, FIG. 1. The water flowthus contacts the portion of the core surrounding each of the openings35 on two opposite sides thereof, thereby increasing the heat exchangeefficiency. By the time the water flow reaches the outlet 58, at least aportion of it has turned to steam and the pumping by the pump 102continues until the steam pressure rises to between 700 and 800 pounds.At this point, a pressure switch 1 10 opens the circuit to the pump 102so as to cut off the flow of water to the flash boiler, thus causing thetemperature of the boiler to increase to between 700 and 800 F. Thisincrease of temperature causes an increase in expansion in the core 30and the rods 62 so as to move the sensing plate 64 out further until theadjusting screw 71 abuts the microswitch 82. A second stage pump iscontinuously driven by the engine (not shown), which in turn is drivenby the steam produced by the boiler. However, until the microswitch 82is activated, the pump empties all of its water back into the water tank106 by a bypass line (not shown). When the microswitch 82 is activated,a solenoid valve switches the flow of the water delivered by the secondstage pump 120 to a line 122 which joins the line 107 coming from thepump 102. The second stage pump 120 then supplies a larger volume to thewater inlet tube 56. The larger volume of flow delivered by the secondstage pump 120 provides a steam pressure between 1,000 and L200 p.s.i.

A second stage pressure switch 124, which could be an additional stagein switch H0, is included to shut off the furnace or combustion chamber94 in the event of pressure delivered by the boiler exceeds 1,200 p.s.i.Also, the furnace or chamber 94 is shut down by the actuation of themicroswitch 83 which is set to occur if for any reason the temperatureof the boiler exceeds between l,000 and 1,100 F. That is, the adjustingscrew 72 is positioned so as to trigger the microswitch 83 when the core30 and the supporting rods 62 have expanded to the point whichrepresents a core temperature of between l,000 and 1,100 F.

Each of the aforedescribed operations is reversible so that when thetemperature or pressure drops, the switches which were closed when thetemperature or pressure rose are reversed so as to reverse the effectthat these switches had.

STACKED CORE EMBODIMENT Referring now to FIGS. 9 through 15, there isillustrated an alternate embodiment wherein a plurality of cores similarto that described in FIGS. 1 through 7 are stacked and utilized togetherto increase the heat exchange between the water flowing through theserpentine path and the hot combustion gases flowing perpendicularlythereto. To clearly identify those portions which perform a functionsimilar to the parts described in connection with the previousembodiment, the same reference numeral is utilized with the addition ofthe number 200.

Thus, a plurality of cores 230a, 230b and 230C are stacked one above theother within a flue pipe 300, the latter being provided with a doublewall formed by the exterior wall 30] to insulate the flue pipe 300from'the exterior. A frame 220 mounts the cores 230a and 2300 by meansof standoff spacers 232 which may be integrally formed therewith. Theopposite end 260 of the cores 230a and 230C are provided with rods 262aand 262b. The rods 262a (FIGS. 9 and 12) are hingedly connected to asensing member 264, whereas the rod 202b is hingedly connected to acontrol member 280. As further hereinafter described, the sensing member264 is also connected with a stabilizing tube 222, the opposite end ofthe tube 222 being hingedly connected to the ends of arms 223 of theframe 220 (FIG. 15).

The flow of the combustion gases is conveyed by the flue pipe 300 in thedirection of arrows 308 through the openings 235 perpendicular to thethree levels established by the parallel cores 230a, b and c.

The cores 230a, 230b and 2300 are identical with the core 30 describedin the previous embodiment with the following exceptions: the headers250 and 252 are each provided (FIG. 10) on the external edges thereofwith fins 253, these fins extending to but not touching the walls of theflue pipe 300. The gaps between the fins 253 and the pipe 300 allowthermal expansion in the transverse direction of the core. Only theheader 252 for core 230s has a water inlet tube 256, and only the header252 for the core 230a has a steam outlet tube 258 (FIG. 9). Theremaining connection from each core to the adjacent core is viaconnecting pipes 259. The connecting pipe 259 joining the serpentinepath of core 230a to that of core 230b joins the latter at the lowerleft-hand comer of the core as shown in FIG. 14. On the other hand, thepipe 259 joins the serpentine path core 2300 with that of 230b byattaching to the latter at the opposite end of the core 2301) (FIG. 13),preferably at the diagonally opposite corner, to prevent shortcircuiting of the water flow.

Thus, the flow of water either as a liquid form or as steam proceedsfrom the inlet tube 256 through the passages 244 in a serpentine path inand out of the plane of the page as viewed in FIG. 13 until the end ofthe core 230c is reached at which point the pipe 259 is connected. Thewater then flows down the pipe 259 and into the next core 230b whereinit traces a serpentine path to the opposite end of that core at thepoint at which pipe 259 connects core 230b to core 230a. The water thenflows into the core 230a to follow the serpentine path in that core. Thewater in the form of steam exits out through tube 258. Thus, the waterflowing in the passageways 244 touches the heat transferring surfaces ofthe openings 235 at a plurality of points discontinuously spaced alongthe length of the passageway for the flue gas through the pipe 300. Bypoints discontinuously spaced along the length, it is meant a spacingdistinguished from a continual spacing along the entire length of thepassageway, so as to indicate instead at discreet locations or levelsonly. It is this repeated exchange of heat by repeated passes of theserpentine path between the passageways of the flue gases which allowsmaximum efiiciency of heat exchange. Also, a counterflow for the waterwith respect to the direction of flow for the hot combustion gasesprovides a maximum temperature differential between the two mediums andthereby a maximum heat transfer.

The control of the boiler of this embodiment is accomplished by thesensing member 264 and the control member 280, which in turn aregenerally flat, cantilevered T-members. The sensing member 264 ishingedly connected by a hinge pin 265 to the control member 280, but italso pivots about a pivot pin 284 which is connected to a stud orplunger 289 that extends into the stabilizing tube 222 to contact acarbon rod 292. This causes the pin 284 to remain in a flxed positionduring boiler operation. The end of the sensing member 264 opposite tothe hinged pin 265 has upstanding lugs 269 (FIG. 12) provided with twotension springs 267 which bias the control member 280 and the sensingmember 264 together (FIG. 10). As in the previous embodiment, adjustingscrews 270, 271 and 272 are spaced along the sensing member 264, but inthis case, they are positioned horizontally rather than vertically. Thecontrol member 280 is also a flat T" member having upstanding lugs 286(FIGS. 10 and 11) similar to the lugs 269 on the sensing member 264, andmounting the opposite end of the springs 267. The control member 280mounts the microswitches 281, 282 and 283 as in the previous embodiment,the positions of the microswitches being opposite to the adjustingscrews 270, 271 and 272. The base 291 of the control member 280 extendstoward the core 230a from the plane defining the support surface for themicroswitches, and

is joined to the sensing member 264 by the hinge pin 265 (FIG. [2).Below the hinge pin 265, the base 291 is joined to the rod 262b by ahinge pin 293.

The operation of this embodiment is identical to the first embodimentdescribed insofar as the basic steps of operation are concerned. Thus,the microswitch 281 is triggered by its abutment with screw 270 when thetemperature reaches between 400 and 500 F., the microswitch 282 istriggered by its abutment with screw 271 when the temperature increasesto between 700 and 800 F., and the microswitch 283 is triggered by itsabutment with 272 when the temperature of the boiler rises to a pointbetween l,OO0 and l,l0O F. However, the operation is somewhat differentinsofar as the relative positions of the control member and the sensingmember are concerned. That is, the fixed point for the sensing member264 is the pivot pin 284. The first of the three cores to expand is thecore 230a, which pushes out on the base 291 to cause the control member280 to pivot inwardly about pin 265 to bring the microswitches towardthe adjusting screws rather than vice versa. The only movement of thesensing member 264 with respect to its original position occurs to aslight extend when the core 230s expands as it begins to heat up, thisexpansion causing the sensing member 264 to pivot about the pin 284 toonly a very slight extent in a clockwise direction as shown in FIG. 9.Thus, the lever formed by the member 264 can be considered to berelatively fixed. The minor movement which it does experience furtherenhances the bringing together of the microswitches and their respectiveabutments with the adjusting screws. Because of the leverage of theconnection between the control member 280 and the sensing member 264, asmall expansion of the cores provides a large relative movement betweenthe microswitches and their abutments with the adjusting screws.

Since the last of the cores 230a to receive the flue gases does so at areduced temperature, that core can be formed from aluminum.

THE CYLINDRICAL CORE EMBODIMENT FIGS. 16 and 17 illustrate yet anotherembodiment wherein the core is wrapped around itself to form acylindrical tube. Parts performing a function similar to those describedin the first embodiment are indicated by the same reference numeral towhich the number 300 has been added.

Thus, the core 330 comprises a cylindrical tubular plate 334 throughwhich flue gas passageways 335 extend on lines radiating from the centeraxis of the core 334. Water passageways 344, of which only several areshown, extend between the columns of passageways 335 and parallel to thecenter axis of the cylindrical tube. The headers 350 and 352 aresimilarly cylindrically bent so as to fit upon the edges of the core334, the water entering into the core through the inlet tube 356 andexiting as steam through the outlet tube 358. The opposite ends of theheader 350 radiate outwardly as arms 361 while the opposite ends ofheader 352 radiate outward as arms 363. Each of the arms 361 parallelsan opposite arm 363, so as to mount either the sensing plate or member364 or the control plate or member 380. The sensing plate member 364 hasmounted thereon adjusting screws 370, 371 and 372, while the controlplate has mounted thereon the respective microswitches of which onlymicroswitch 381 is shown.

Because the core 330 is cylindrical, it is possible to incorporate thecombustion chamber 394 within the core. In that case, the pipe 395 isthe firing gun for the combustion chamber and is positioned near one endof the cylindrical core so as to allow the combustion to occursubstantially along the entire length of the core. Or, the combustionchamber can be removed from the core and in that case, the pipe 395 is aportion of the fuel pipe coming from the combustion chamber. In eithercase, the end opposite to the pipe 395 is closed off and the combustiongases are carried away from the exterior of the core 330 by flue pipesnot shown.

Because of the slight gap between the ends of the core plate 334provided for thermal expansion, it is necessary to provide a sealingplate 398 (FIG. 17) which is fixed to at most only one of the two endsof the core 334.

The operation of the cylindrical core embodiment is exactly that of thefirst embodiment, except that as the core 330 expands, the cylindricaltube formed thereby tends to open upon itself, thereby causing thesensing plate 364 and the control plate 380 to depart each other so asto activate the microswitches at difierent points in the approach ascontrolled by the thennal expansion and the different settings of theadjustment screws. If desired, one of the plates 364 and 380 may befixed, so as to cause the other to move during thermal expansion. Thewater flow through passageways 344 turns around in the headers 350 and352 in the same manner as the previous embodiments.

It will be readily recognized that one advantage of the cylindricalembodiment is that it does away with the need for a frame such as frame20 or 220 and for the stabilizing tubes 22 or 222.

Although the invention has been described in connection with severalpreferred embodiments, it will be readily appreciated that modificationscan be made within the scope of this invention, For example, if stackedcores are to be utilized, any number of cores can be so stacked. Also,where a stack has been shown to be vertical so that the flow of thewater through any one core is horizontal, the entire arrangement can berotated 90 so as to arrange the stack horizontally. Furthermore, anyorientation of the cores can be utilized inasmuch as the orientationwith respect to the steam engine driven by the boiler is not important.Finally, it is not necessary that the microswitches be relativelypositioned so that the next to be activated as the combustion chamberand core heat up is the next adjacent switch. Thus, with reference tothe first embodiment, the microswitch 83 could be the switch whichactivates the second stage pump whereas the microswitch 82 whenactivated shuts down the combustion chamber. In that case, the adjustingscrews are positioned so as to be the proper distance from themicroswitch. Also, additional microswitches can be added to the controlplate or member along with appropriate abutting adjusting screws toperform other control functions, if desired. With respect to themicroswitches and their respective adjustment screws, the controllingrequirement is that each adjustment screw abuts one of the microswitchesat a point in the thermal expansion of the core which is different fromthe point at which any other microswitch is abutted by its adjustingscrew.

Thus, it is intended that the invention include as well alternateequivalent embodiments unless expressly stated otherwise in thefollowing claims.

The embodiments of the invention in which an exclusive property orprivilege is claimed are defined as follows.

1. In a heat exchanger for transferring heat from a first medium to asecond medium, the exchanger including a set of passageways havingexternal heat-exchanging surfaces and confining the flow of the firstand second mediums in the vicinity of each other; the improvementcomprising said passageways for one of the mediums each being positionedto confine the flow of said one medium to a nonlinear path whichcontacts said surfaces of substantially all of said passageways for theother of said mediums on at least two opposite sides, said passagewaysfor said one medium forming a serpentine path for the flow of said onemedium, and said passageways for said other medium comprising aplurality of nonconnecting openings in a core.

2. The improved heat exchanger as defined in claim 1, wherein said eachof said openings extend approximately perpendicular to the direction offlow of said path at any point of said path which is in the heatexchanging vicinity of said each opening.

3. The improved heat exchanger as defined in claim 2, wherein said coreis planar and otherwise solid, said passageways for said one medium andsaid serpentine path are both drilled into said core, and said openingsare parallel to each other.

4. The improved heat exchanger as defined in claim 2, wherein saidpassageways for said one medium and said serpentine path are bothconfined to said core, said core is a cylindrical tube, and said pipespass therethrough along radial lines radiating from the axis of saidcore.

5. The improved heat exchanger as defined in claim 1, wherein said pathis confined within a solid metallic core one end of which is especiallyadapted to move away from its original position when said core isheated, and further including means for controlling the operation of theexchanger, said controlling means including sensing means positioned tosense said core end in its moved state.

6. The improved heat exchanger as defined in claim 5, and furtherincluding means for mounting said controlling means and said core on thesame frame.

7. The improved heat exchanger as defined in claim 6, wherein saidmounting means includes a rod in contact with said sensing means andhaving a coefficient of thennal expansion which is as low as that ofcarbon.

8. The improved heat exchanger as defined in claim 5, wherein saidcontrolling means includes a generally planar member and at least twomicroswitches on said member, and said sensing means includes adjustableabutments for contacting said switches, each of said abutments beingadjusted so as to abut its respective microswitch at a point in saidmovement of said end which is different from the point at which anotherof said microswitches is abutted.

9. The improved heat exchanger as defined in claim 8, wherein theexchanger is a flash boiler, said one medium is water and steam, saidother medium is hot flue or combustion gases supplied by a combustionchamber, and said abutments are so adjusted that the first to contactits respective microswitch activates a source of supply of the waterwhile the last to contact its microswitch deactivates the combustionchamber.

10. in a heat exchanger for transferring heat from a first medium to asecond medium, the exchanger including a set of passageways havingexternal heat-exchanging surfaces and confining the flow of the firstand second mediums in the vicinity of each other; the improvementcomprising said passageways for one of the mediums each being positionedto confine the flow of said one medium to a nonlinear path whichcontacts said surfaces of substantially all of said passageways for theother of said mediums on at least two opposite sides, said nonlinearpath of said passageways of said one medium forming a plurality ofconnected, stacked levels, and said passageways for the other of saidmediums penetrating all of said levels, whereby said one medium flowsthrough said path sequentially from one level to the next so as torepeat its heat exchange with said other medium on each level.

11. The improved heat exchanger as defined in claim 10, wherein the flowof said one medium through said path proceeds from the first of saidlevels to the last, while the flow of said other medium through saidpassageways passes first through said last of said levels and lastlythrough said first of said levels.

12. The improved heat exchanger as defined in claim 10, wherein saidlevels are planar cores.

13. The improved heat exchanger as defined in claim 12, wherein theplanes of said cores are parallel.

14. The improved heat exchanger as defined in claim 12, wherein at leastone of said cores is metallic and has one end of which is especiallyadapted to move outwardly away from its original position when said onecore is heated, and further including means for controlling the flow ofthe mediums through said passageways, said controlling means beingoperatively connected to said end of at least said one core.

15. The improved heat exchanger as defined in claim 14, and furtherincluding means for sensing certain predetermined outward movements ofsaid core end, said sensing means including a first cantilevered memberhingedly connected to at least one of said cores.

16. The improved heat exchanger as defined in claim 15, wherein saidsensing means further includes a second cantilevered member hingedlyconnected at one end to said first member, a spring biasing saidcantilevered members together at their ends opposite to said hingedlyconnected end, and mounting means for fixedly mounting one of saidmembers so as to provide a reference surface for sensing saidpredetermined movement.

17. The improved heat exchanger as defined in claim 16, wherein said onemember includes at least two adjustable abutments and said controllingmeans includes at least two microswitches mounted on the other of saidmembers, each of said abutments being adjusted so as to abut one of saidmicroswitches at a point in said movement which is different from thepoint at which another of said microswitches is abutted.

18. The improved heat exchanger as defined in claim 17, wherein theexchanger is a flash boiler, said one medium is water and steam, saidother medium is hot flue or combustion gases supplied by a combustionchamber, and said abutments are so adjusted that the first to contactits respective microswitch activates a source of supply of the waterwhile the last to contact its microswitch deactivates the combustionchamber.

19. The improved heat exchanger as defined in claim 16, wherein saidmounting means includes a stud hingedly connected to said one member,and a rod in contact with said stud and having a coefficient of thermalexpansion which is as low as that of carbon.

20. in a flash boiler, a plurality of heat exchanger passageways havingexternal heat-transferring surfaces, one set of which conducts a firstmedium .and the'remainder of which conducts a second medium, one of saidmediums being water, said one set being positioned to form a nonlinear,nonplanar path which contacts said surfaces of each of said passagewaysof said second set at a plurality of points discontinuously spaced alongthe length of each of said second set of passageways, the direction offlow of said mediums being adapted to maintain a maximum temperaturedifferential between the two, whereby heat is transferred from one ofsaid mediums to the water; and sensing means for sensing the amount ofthermal expansion of said surfaces due to the heat of the other of saidmediums which has not been absorbed by the water in forming steam.

21. The boiler as defined in claim 20, wherein said one set ofpassageways traces a serpentine path through a plurality of stackedcores each of which defines a plane, and said remainder of saidpassageways includes a plurality of openings extending approximatelyperpendicularly through said each core, said path contacting at leastonce said surfaces surrou nding each of said openings in said each core;a connecting pipe between each adjacent pair of said cores and incommunication with said path in said pair of cores; a passagewayconnecting said openings in said each core with said openings in eachadjacent core, whereby hot gases flowing approximately perpendicularlythrough a first of said cores will generally flow through each adjacentof said cores in turn; and wherein said sensing means is mounted on saidfirst core.

22. The boiler as defined in claim 21, wherein said sensing meansincludes a rod projecting from one end of said first core and a leverhingedly connected to said rod, said lever being hinged also to arelatively fixed reference point.

23. The boiler as defined in claim 22, wherein said lever is hingedlyconnected to said rod near one of its ends, and to said reference pointbetween said rod connection ad the opposite end of said lever.

24. The boiler as defined in claim 22, and further including a pluralityof microswitches mounted on said lever, each of which is especiallyadapted to be triggered by predetermined movement of said lever asmeasured from a reference position, the triggering movement for eachmicroswitch differing from that of the others.

25. The boiler as defined in claim 21, wherein said path passes the coreportions surrounding each of said openings in said each core on twoopposite sides thereof.

26. In a heat exchanger including a core having a plurality ofpassageways for conducting both a hot medium and a cold medium for theexchange of heat between the two, the improvement comprising sensingmeans positioned adjacent to the end of said core for sensingdimensional changes of the same due to the operation of the exchanger,controlling means operatively connected to said sensing means forcontrolling the amount of the hot and cold mediums to be supplied tosaid passageways in response to said changes; said sensing meansincluding two generally flat members, one of which includes means forrelatively fixedly mounting the same and the other of which isoperatively connected to said core end for movement with respect to saidone member.

27. The improved heat exchanger as defined in claim 26, wherein saidcontrolling means includes at least two microswitches on said othermember and said sensing means includes at least two adjustable abutmentson said one member, each of which is adjusted so as to abut one of saidmicroswitches at a point in said movement of said other member which isdifferent from the point at which another of said microswitches isabutted.

28. The improved heat exchanger as defined in claim 27, wherein said twomembers are hingedly connected together near one end and connected attheir opposite ends by a spring.

29. The improved heat exchanger as defined in claim 28, wherein saidconnection of said other member to said core is positioned so that saidhinged connection is between said core connection and said springconnection.

30. The improved heat exchanger as defined in claim 27, wherein theexchanger is'a flash boiler, said cold medium is water, said hot mediumis flue or combustion gases supplied by a combustion chamber, and saidabutments are so adjusted that the first to contact its respectivemicroswitch activates a source of supply of the water while the last tocontact its microswitch deactivates the combustion chamber.

31. The improved heat exchanger as defined in claim 26, wherein saidcore is generally cylindrical and said members extend outwardlytherefrom in planes radiating from the axis of said core.

32. The improved heat exchanger as defined in claim 31, wherein said onemember is attached to the opposite end of said core.

33. In a heat exchanger including a core having a plurality ofpassageways for conducting both a hot medium and a cold medium for theexchange of heat between the two, the improvement comprising sensingmeans positioned adjacent to the end of said core for sensingdimensional changes of the same due to the operation of the exchanger,controlling means operatively connected to said sensing means forcontrolling the amount of the hot and cold mediums to be supplied tosaid passageways in response to said changes; said sensing meansincluding a rod projecting from one end of said core and a leverhingedly connected to said rod, said lever being hinged also to arelatively fixed reference point.

34. The improved heat exchanger as defined in claim 33, wherein saidlever is hingedly connected to said rod near one of its ends, and tosaid reference point between said rod connection and the opposite end ofsaid lever.

35. The improved heat exchanger as defined in claim 33, and furtherincluding a plurality of microswitches mounted on said lever, each ofwhich is especially adapted to be triggered by predetermined movement ofsaid lever as measured from a reference position, the triggeringmovement for each microswitch differing from that of the others.

i i t i

1. In a heat exchanger for transferring heat from a first medium to asecond medium, the exchanger including a set of passageways havingexternal heat-exchanging surfaces and confining the flow of the firstand second mediums in the vicinity of each other; the improvementcomprising said passageways for one of the mediums each being positionedto confine the flow of said one medium to a nonlinear path whichcontacts said surfaces of substantially all of said passageways for theother of said mediums on at least two opposite sides, said passagewaysfor said one medium forming a serpentine path for the flow of said onemedium, and said passageways for said other medium comprising aplurality of nonconnecting openings in a core.
 2. The improved heatexchanger as defined in claim 1, wherein said each of said openingsextend approximately perpendicular to the direction of flow of said pathat any point of said path which is in the heat exchanging vicinity ofsaid each opening.
 3. The improved heat exchanger as defined in claim 2,wherein said core is planar and otherwise solid, said passageways forsaid one medium and said serpentine path are both drilled into saidcore, and said openings are parallel to each other.
 4. The improved heatexchanger as dEfined in claim 2, wherein said passageways for said onemedium and said serpentine path are both confined to said core, saidcore is a cylindrical tube, and said pipes pass therethrough alongradial lines radiating from the axis of said core.
 5. The improved heatexchanger as defined in claim 1, wherein said path is confined within asolid metallic core one end of which is especially adapted to move awayfrom its original position when said core is heated, and furtherincluding means for controlling the operation of the exchanger, saidcontrolling means including sensing means positioned to sense said coreend in its moved state.
 6. The improved heat exchanger as defined inclaim 5, and further including means for mounting said controlling meansand said core on the same frame.
 7. The improved heat exchanger asdefined in claim 6, wherein said mounting means includes a rod incontact with said sensing means and having a coefficient of thermalexpansion which is as low as that of carbon.
 8. The improved heatexchanger as defined in claim 5, wherein said controlling means includesa generally planar member and at least two microswitches on said member,and said sensing means includes adjustable abutments for contacting saidswitches, each of said abutments being adjusted so as to abut itsrespective microswitch at a point in said movement of said end which isdifferent from the point at which another of said microswitches isabutted.
 9. The improved heat exchanger as defined in claim 8, whereinthe exchanger is a flash boiler, said one medium is water and steam,said other medium is hot flue or combustion gases supplied by acombustion chamber, and said abutments are so adjusted that the first tocontact its respective microswitch activates a source of supply of thewater while the last to contact its microswitch deactivates thecombustion chamber.
 10. In a heat exchanger for transferring heat from afirst medium to a second medium, the exchanger including a set ofpassageways having external heat-exchanging surfaces and confining theflow of the first and second mediums in the vicinity of each other; theimprovement comprising said passageways for one of the mediums eachbeing positioned to confine the flow of said one medium to a nonlinearpath which contacts said surfaces of substantially all of saidpassageways for the other of said mediums on at least two oppositesides, said nonlinear path of said passageways of said one mediumforming a plurality of connected, stacked levels, and said passagewaysfor the other of said mediums penetrating all of said levels, wherebysaid one medium flows through said path sequentially from one level tothe next so as to repeat its heat exchange with said other medium oneach level.
 11. The improved heat exchanger as defined in claim 10,wherein the flow of said one medium through said path proceeds from thefirst of said levels to the last, while the flow of said other mediumthrough said passageways passes first through said last of said levelsand lastly through said first of said levels.
 12. The improved heatexchanger as defined in claim 10, wherein said levels are planar cores.13. The improved heat exchanger as defined in claim 12, wherein theplanes of said cores are parallel.
 14. The improved heat exchanger asdefined in claim 12, wherein at least one of said cores is metallic andhas one end of which is especially adapted to move outwardly away fromits original position when said one core is heated, and furtherincluding means for controlling the flow of the mediums through saidpassageways, said controlling means being operatively connected to saidend of at least said one core.
 15. The improved heat exchanger asdefined in claim 14, and further including means for sensing certainpredetermined outward movements of said core end, said sensing meansincluding a first cantilevered member hingedly connected to at least oneof said cores.
 16. The improved heat exchanger as defined in claim 15,Wherein said sensing means further includes a second cantilevered memberhingedly connected at one end to said first member, a spring biasingsaid cantilevered members together at their ends opposite to saidhingedly connected end, and mounting means for fixedly mounting one ofsaid members so as to provide a reference surface for sensing saidpredetermined movement.
 17. The improved heat exchanger as defined inclaim 16, wherein said one member includes at least two adjustableabutments and said controlling means includes at least two microswitchesmounted on the other of said members, each of said abutments beingadjusted so as to abut one of said microswitches at a point in saidmovement which is different from the point at which another of saidmicroswitches is abutted.
 18. The improved heat exchanger as defined inclaim 17, wherein the exchanger is a flash boiler, said one medium iswater and steam, said other medium is hot flue or combustion gasessupplied by a combustion chamber, and said abutments are so adjustedthat the first to contact its respective microswitch activates a sourceof supply of the water while the last to contact its microswitchdeactivates the combustion chamber.
 19. The improved heat exchanger asdefined in claim 16, wherein said mounting means includes a studhingedly connected to said one member, and a rod in contact with saidstud and having a coefficient of thermal expansion which is as low asthat of carbon.
 20. In a flash boiler, a plurality of heat exchangerpassageways having external heat-transferring surfaces, one set of whichconducts a first medium and the remainder of which conducts a secondmedium, one of said mediums being water, said one set being positionedto form a nonlinear, nonplanar path which contacts said surfaces of eachof said passageways of said second set at a plurality of pointsdiscontinuously spaced along the length of each of said second set ofpassageways, the direction of flow of said mediums being adapted tomaintain a maximum temperature differential between the two, wherebyheat is transferred from one of said mediums to the water; and sensingmeans for sensing the amount of thermal expansion of said surfaces dueto the heat of the other of said mediums which has not been absorbed bythe water in forming steam.
 21. The boiler as defined in claim 20,wherein said one set of passageways traces a serpentine path through aplurality of stacked cores each of which defines a plane, and saidremainder of said passageways includes a plurality of openings extendingapproximately perpendicularly through said each core, said pathcontacting at least once said surfaces surrounding each of said openingsin said each core; a connecting pipe between each adjacent pair of saidcores and in communication with said path in said pair of cores; apassageway connecting said openings in said each core with said openingsin each adjacent core, whereby hot gases flowing approximatelyperpendicularly through a first of said cores will generally flowthrough each adjacent of said cores in turn; and wherein said sensingmeans is mounted on said first core.
 22. The boiler as defined in claim21, wherein said sensing means includes a rod projecting from one end ofsaid first core and a lever hingedly connected to said rod, said leverbeing hinged also to a relatively fixed reference point.
 23. The boileras defined in claim 22, wherein said lever is hingedly connected to saidrod near one of its ends, and to said reference point between said rodconnection ad the opposite end of said lever.
 24. The boiler as definedin claim 22, and further including a plurality of microswitches mountedon said lever, each of which is especially adapted to be triggered bypredetermined movement of said lever as measured from a referenceposition, the triggering movement for each microswitch differing fromthat of the others.
 25. The boiler as defined in claim 21, wherein saidpath passes the core portions surrounding each of said openIngs in saideach core on two opposite sides thereof.
 26. In a heat exchangerincluding a core having a plurality of passageways for conducting both ahot medium and a cold medium for the exchange of heat between the two,the improvement comprising sensing means positioned adjacent to the endof said core for sensing dimensional changes of the same due to theoperation of the exchanger, controlling means operatively connected tosaid sensing means for controlling the amount of the hot and coldmediums to be supplied to said passageways in response to said changes;said sensing means including two generally flat members, one of whichincludes means for relatively fixedly mounting the same and the other ofwhich is operatively connected to said core end for movement withrespect to said one member.
 27. The improved heat exchanger as definedin claim 26, wherein said controlling means includes at least twomicroswitches on said other member and said sensing means includes atleast two adjustable abutments on said one member, each of which isadjusted so as to abut one of said microswitches at a point in saidmovement of said other member which is different from the point at whichanother of said microswitches is abutted.
 28. The improved heatexchanger as defined in claim 27, wherein said two members are hingedlyconnected together near one end and connected at their opposite ends bya spring.
 29. The improved heat exchanger as defined in claim 28,wherein said connection of said other member to said core is positionedso that said hinged connection is between said core connection and saidspring connection.
 30. The improved heat exchanger as defined in claim27, wherein the exchanger is a flash boiler, said cold medium is water,said hot medium is flue or combustion gases supplied by a combustionchamber, and said abutments are so adjusted that the first to contactits respective microswitch activates a source of supply of the waterwhile the last to contact its microswitch deactivates the combustionchamber.
 31. The improved heat exchanger as defined in claim 26, whereinsaid core is generally cylindrical and said members extend outwardlytherefrom in planes radiating from the axis of said core.
 32. Theimproved heat exchanger as defined in claim 31, wherein said one memberis attached to the opposite end of said core.
 33. In a heat exchangerincluding a core having a plurality of passageways for conducting both ahot medium and a cold medium for the exchange of heat between the two,the improvement comprising sensing means positioned adjacent to the endof said core for sensing dimensional changes of the same due to theoperation of the exchanger, controlling means operatively connected tosaid sensing means for controlling the amount of the hot and coldmediums to be supplied to said passageways in response to said changes;said sensing means including a rod projecting from one end of said coreand a lever hingedly connected to said rod, said lever being hinged alsoto a relatively fixed reference point.
 34. The improved heat exchangeras defined in claim 33, wherein said lever is hingedly connected to saidrod near one of its ends, and to said reference point between said rodconnection and the opposite end of said lever.
 35. The improved heatexchanger as defined in claim 33, and further including a plurality ofmicroswitches mounted on said lever, each of which is especially adaptedto be triggered by predetermined movement of said lever as measured froma reference position, the triggering movement for each microswitchdiffering from that of the others.